The invention relates to a cathode ray tube having an envelope and an electromagnetic deflection unit which coaxially surrounds a part of the envelope and which comprises a flared coil support. A deflection coil system is positioned between the coil support and the envelope, and comprises a pair of diametrically opposite coils, each of which fans out, and packs of conductors which surround a window and which form a front flange at the wide end portion and a rear flange at the narrow end portion.
The invention further relates to a deflection unit which is suitable for use in such a cathode ray tube.
Such a cathode ray tube can be used in colour television, data-display devices and in other devices in which a cathode ray tube is used.
In the energized state, the deflection unit deflects electron beams generated in the envelope in mutually orthogonal directions to form an image to be displayed. Preferably, the deflection coil system is located as close to the envelope as possible to minimize the energy necessary for deflecting the electron beams. Such energy is proportional to the magnitude of the electric current which is necessary during energizing the deflection unit to bring about sufficient deflection, and is governed by the distance between deflection coil system and electron beams.
In practice, however, it may occur that despite the carefully determined position of the packs of conductors of the deflection coil system, the convergence of electron beams generated in the neck portion is not always sufficient during deflection.